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Commit f56c5a36 authored by Adam Barth's avatar Adam Barth Committed by GitHub
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Move ViewportOffset to its own file (#7840) 

There aren't any interdependencies with the rest of sliver.dart, and that file
is already quite complex.
parent 32314657
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Showing with 147 additions and 138 deletions
packages/flutter/lib/rendering.dart
View file @ f56c5a36
......@@ -55,6 +55,7 @@ export 'src/rendering/stack.dart';
export 'src/rendering/table.dart';
export 'src/rendering/tweens.dart';
export 'src/rendering/view.dart';
export 'src/rendering/viewport_offset.dart';
export 'src/rendering/viewport.dart';
export 'package:flutter/foundation.dart' show
......
packages/flutter/lib/src/rendering/sliver.dart
View file @ f56c5a36
......@@ -13,6 +13,7 @@ import 'box.dart';
import 'binding.dart';
import 'debug.dart';
import 'object.dart';
import 'viewport_offset.dart';
// CORE TYPES FOR SLIVERS
// The RenderSliver base class and its helper types.
......@@ -41,33 +42,6 @@ enum GrowthDirection {
reverse,
}
/// The direction of a scroll, relative to the positive scroll offset axis given
/// by an [AxisDirection] and a [GrowthDirection].
///
/// This contrasts to [GrowthDirection] in that it has a third value, [idle],
/// for the case where no scroll is occurring.
///
/// This is used by [RenderSliverFloatingAppBar] to only expand when the user is
/// scrolling in the same direction as the detected scroll offset change.
enum ScrollDirection {
/// No scrolling is underway.
idle,
/// Scrolling is happening in the positive scroll offset direction.
///
/// For example, for the [GrowthDirection.forward] part of a vertical
/// [AxisDirection.down] list, this means the content is moving up, exposing
/// lower content.
forward,
/// Scrolling is happening in the negative scroll offset direction.
///
/// For example, for the [GrowthDirection.forward] part of a vertical
/// [AxisDirection.down] list, this means the content is moving down, exposing
/// earlier content.
reverse,
}
enum AxisDirection {
/// Zero is at the bottom and positive values are above it: ⇈
///
......@@ -1094,117 +1068,6 @@ abstract class RenderSliverHelpers implements RenderSliver {
typedef RenderSliver _Advancer(RenderSliver child);
abstract class ViewportOffset extends ChangeNotifier {
ViewportOffset();
factory ViewportOffset.fixed(double value) = _FixedViewportOffset;
factory ViewportOffset.zero() = _FixedViewportOffset.zero;
/// The number of pixels to offset the children in the opposite of the axis direction.
///
/// For example, if the axis direction is down, then the pixel value
/// represents the number of logical pixels to move the children _up_ the
/// screen. Similarly, if the axis direction is left, then the pixels value
/// represents the number of logical pixesl to move the children to _right_.
double get pixels;
/// Called when the viewport's extents are established.
///
/// The argument is the dimension of the [RenderViewport2] in the main axis
/// (e.g. the height, for a vertical viewport).
///
/// This may be called redundantly, with the same value, each frame. This is
/// called during layout for the [RenderViewport2]. If the viewport is
/// configured to shrink-wrap its contents, it may be called several times,
/// since the layout is repeated each time the scroll offset is corrected.
///
/// If this is called, it is called before [applyContentDimensions]. If this
/// is called, [applyContentDimensions] will be called soon afterwards in the
/// same layout phase. If the viewport is not configured to shrink-wrap its
/// contents, then this will only be called when the viewport recomputes its
/// size (i.e. when its parent lays out), and not during normal scrolling.
void applyViewportDimension(double viewportDimension);
/// Called when the viewport's content extents are established.
///
/// The arguments are the minimum and maximum scroll extents respectively. The
/// minimum will be equal to or less than zero, the maximum will be equal to
/// or greater than zero.
///
/// The maximum scroll extent has the viewport dimension subtracted from it.
/// For instance, if there is 100.0 pixels of scrollable content, and the
/// viewport is 80.0 pixels high, then the minimum scroll extent will
/// typically be 0.0 and the maximum scroll extent will typically be 20.0,
/// because there's only 20.0 pixels of actual scroll slack.
///
/// If applying the content dimensions changes the scroll offset, return
/// false. Otherwise, return true. If you return false, the [RenderViewport2]
/// will be laid out again with the new scroll offset. This is expensive. (The
/// return value is answering the question "did you accept these content
/// dimensions unconditionally?"; if the new dimensions change the
/// [ViewportOffset]'s actual [pixels] value, then the viewport will need to
/// be laid out again.)
///
/// This is called at least once each time the [RenderViewport2] is laid out,
/// even if the values have not changed. It may be called many times if the
/// scroll offset is corrected (if this returns false). This is always called
/// after [applyViewportDimension], if that method is called.
bool applyContentDimensions(double minScrollExtent, double maxScrollExtent);
/// Apply a layout-time correction to the scroll offset.
///
/// This method should change the [pixels] value by `correction`, but without
/// calling [notifyListeners]. It is called during layout by the
/// [RenderViewport2], before [applyContentDimensions]. After this method is
/// called, the layout will be recomputed and that may result in this method
/// being called again, though this should be very rare.
void correctBy(double correction);
/// The direction in which the user is trying to change [pixels], relative to
/// the viewport's [RenderViewport2.axisDirection].
///
/// This is used by some slivers to determine how to react to a change in
/// scroll offset. For example, [RenderSliverFloatingAppBar] will only expand
/// a floating app bar when the [userScrollDirection] is in the positive
/// scroll offset direction.
ScrollDirection get userScrollDirection;
@override
String toString() {
final List<String> description = <String>[];
debugFillDescription(description);
return '$runtimeType(${description.join(", ")})';
}
@mustCallSuper
void debugFillDescription(List<String> description) {
description.add('offset: ${pixels.toStringAsFixed(1)}');
}
}
class _FixedViewportOffset extends ViewportOffset {
_FixedViewportOffset(this._pixels);
_FixedViewportOffset.zero() : _pixels = 0.0;
double _pixels;
@override
double get pixels => _pixels;
@override
void applyViewportDimension(double viewportDimension) { }
@override
bool applyContentDimensions(double minScrollExtent, double maxScrollExtent) => true;
@override
void correctBy(double correction) {
_pixels += correction;
}
@override
ScrollDirection get userScrollDirection => ScrollDirection.idle;
}
// ///
// /// See also:
// ///
......
packages/flutter/lib/src/rendering/sliver_app_bar.dart
View file @ f56c5a36
......@@ -13,6 +13,7 @@ import 'box.dart';
import 'binding.dart';
import 'object.dart';
import 'sliver.dart';
import 'viewport_offset.dart';
abstract class RenderSliverAppBar extends RenderSliver with RenderObjectWithChildMixin<RenderBox>, RenderSliverHelpers {
RenderSliverAppBar({ RenderBox child }) {
......
packages/flutter/lib/src/rendering/viewport_offset.dart 0 → 100644
View file @ f56c5a36
// Copyright 2016 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
import 'package:flutter/foundation.dart';
import 'package:meta/meta.dart';
/// The direction of a scroll, relative to the positive scroll offset axis given
/// by an [AxisDirection] and a [GrowthDirection].
///
/// This contrasts to [GrowthDirection] in that it has a third value, [idle],
/// for the case where no scroll is occurring.
///
/// This is used by [RenderSliverFloatingAppBar] to only expand when the user is
/// scrolling in the same direction as the detected scroll offset change.
enum ScrollDirection {
/// No scrolling is underway.
idle,
/// Scrolling is happening in the positive scroll offset direction.
///
/// For example, for the [GrowthDirection.forward] part of a vertical
/// [AxisDirection.down] list, this means the content is moving up, exposing
/// lower content.
forward,
/// Scrolling is happening in the negative scroll offset direction.
///
/// For example, for the [GrowthDirection.forward] part of a vertical
/// [AxisDirection.down] list, this means the content is moving down, exposing
/// earlier content.
reverse,
}
abstract class ViewportOffset extends ChangeNotifier {
ViewportOffset();
factory ViewportOffset.fixed(double value) = _FixedViewportOffset;
factory ViewportOffset.zero() = _FixedViewportOffset.zero;
/// The number of pixels to offset the children in the opposite of the axis direction.
///
/// For example, if the axis direction is down, then the pixel value
/// represents the number of logical pixels to move the children _up_ the
/// screen. Similarly, if the axis direction is left, then the pixels value
/// represents the number of logical pixesl to move the children to _right_.
double get pixels;
/// Called when the viewport's extents are established.
///
/// The argument is the dimension of the [RenderViewport2] in the main axis
/// (e.g. the height, for a vertical viewport).
///
/// This may be called redundantly, with the same value, each frame. This is
/// called during layout for the [RenderViewport2]. If the viewport is
/// configured to shrink-wrap its contents, it may be called several times,
/// since the layout is repeated each time the scroll offset is corrected.
///
/// If this is called, it is called before [applyContentDimensions]. If this
/// is called, [applyContentDimensions] will be called soon afterwards in the
/// same layout phase. If the viewport is not configured to shrink-wrap its
/// contents, then this will only be called when the viewport recomputes its
/// size (i.e. when its parent lays out), and not during normal scrolling.
void applyViewportDimension(double viewportDimension);
/// Called when the viewport's content extents are established.
///
/// The arguments are the minimum and maximum scroll extents respectively. The
/// minimum will be equal to or less than zero, the maximum will be equal to
/// or greater than zero.
///
/// The maximum scroll extent has the viewport dimension subtracted from it.
/// For instance, if there is 100.0 pixels of scrollable content, and the
/// viewport is 80.0 pixels high, then the minimum scroll extent will
/// typically be 0.0 and the maximum scroll extent will typically be 20.0,
/// because there's only 20.0 pixels of actual scroll slack.
///
/// If applying the content dimensions changes the scroll offset, return
/// false. Otherwise, return true. If you return false, the [RenderViewport2]
/// will be laid out again with the new scroll offset. This is expensive. (The
/// return value is answering the question "did you accept these content
/// dimensions unconditionally?"; if the new dimensions change the
/// [ViewportOffset]'s actual [pixels] value, then the viewport will need to
/// be laid out again.)
///
/// This is called at least once each time the [RenderViewport2] is laid out,
/// even if the values have not changed. It may be called many times if the
/// scroll offset is corrected (if this returns false). This is always called
/// after [applyViewportDimension], if that method is called.
bool applyContentDimensions(double minScrollExtent, double maxScrollExtent);
/// Apply a layout-time correction to the scroll offset.
///
/// This method should change the [pixels] value by `correction`, but without
/// calling [notifyListeners]. It is called during layout by the
/// [RenderViewport2], before [applyContentDimensions]. After this method is
/// called, the layout will be recomputed and that may result in this method
/// being called again, though this should be very rare.
void correctBy(double correction);
/// The direction in which the user is trying to change [pixels], relative to
/// the viewport's [RenderViewport2.axisDirection].
///
/// This is used by some slivers to determine how to react to a change in
/// scroll offset. For example, [RenderSliverFloatingAppBar] will only expand
/// a floating app bar when the [userScrollDirection] is in the positive
/// scroll offset direction.
ScrollDirection get userScrollDirection;
@override
String toString() {
final List<String> description = <String>[];
debugFillDescription(description);
return '$runtimeType(${description.join(", ")})';
}
@mustCallSuper
void debugFillDescription(List<String> description) {
description.add('offset: ${pixels.toStringAsFixed(1)}');
}
}
class _FixedViewportOffset extends ViewportOffset {
_FixedViewportOffset(this._pixels);
_FixedViewportOffset.zero() : _pixels = 0.0;
double _pixels;
@override
double get pixels => _pixels;
@override
void applyViewportDimension(double viewportDimension) { }
@override
bool applyContentDimensions(double minScrollExtent, double maxScrollExtent) => true;
@override
void correctBy(double correction) {
_pixels += correction;
}
@override
ScrollDirection get userScrollDirection => ScrollDirection.idle;
}
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